The present invention generally relates to a catamenial tampon having a multi-layered cover and an absorbent core. The outer surface of the cover is wettable to provide a moist surface against the vaginal wall, while inner regions of the cover disrupt immediate liquid flow into the absorbent core. This structure decreases the likelihood that the tampon will desiccate the surface of the vaginal wall.
Catamenial tampons are generally used to absorb menstrual fluid of women during the menstrual cycle. Usually, menstrual flow varies during the cycle, and there are often days of relatively light flow at the beginning and end of the cycle. On light flow days, there is little excess fluid available for a tampon to absorb in the vaginal cavity, and conventional tampons may absorb too much fluid, desiccating the vaginal wall or mucosa. This can cause discomfort during the insertion and removal of these tampons.
The area of the vaginal cavity of major concern relating to the desiccation is the upper layer of cells in the vaginal mucosa, the squamous epithelium. Under non-menstrual conditions, the vaginal wall is lubricated by secretions that pass through the vagina: fluids and mucus flowing from the cervix and hormone-controlled secretions originating in the uterus. The natural exfoliation of vaginal epithelial cells also contributes to the natural moisture in the vaginal cavity and the squamous epithelium.
When a conventional tampon absorbs the natural moisture from between the cells in the squamous epithelium on light flow days of the menstrual cycle, the cells are rendered more susceptible to being peeled off prematurely. This peeling is called desquamation, and it can occur in removal of the tampon prior to its saturation. First, the initial release of an unsaturated conventional tampon can be quite painful, as some of the squamous cells may have become xe2x80x9cattachedxe2x80x9d to the conventional tampon as it absorbs the natural moisture. Next, the dry, absorbent surface of the conventional tampon can drag along other portions of the relatively dry squamous epithelium causing additional pain.
These conventional tampons often have a cover disposed on the majority of the surface of the absorbent structure to contain absorbent materials therein. An example of such a cover can be seen in Friese, U.S. Pat. No. 4,816,100, which uses a nonwoven cover. Several attempts have been made to improve tampon covers. One attempt is illustrated in Jackson, U.S. Pat. No. 4,305,391, which employs a combination of two wrapping layers to form a cover. The outer wrap has a substantially greater pore size than the inner wrap. Purportedly, this allows fluid to rapidly pass through the outer wrap before it is partially absorbed and more slowly passed through the inner wrap of the cover. This arrangement of a porosity gradient or suction gradient is conventionally used to better isolate fluids within the tampon to reduce reverse flow from the absorbent core to the surface of the cover.
Another attempt to reduce the pain associated with the removal of tampons is disclosed in Jackson, U.S. Pat. No. 4,335,722. This attempt employs a water dispersible barrier layer around a strongly absorbent core containing superabsorbent material. This absorbent structure is then covered with a non-superabsorbent material, such as rayon. In this construction, the absorbent core is utilized only after the outer layer is saturated. Then, fluid from the saturated cover is available to disperse the barrier layer. However, once the barrier layer is dispersed, a conventional suction pressure gradient draws fluid into the core from the cover.
Finally, Kaczmarzyk et al., U.S. Pat. No. 4,056,103, discloses a fluid-permeable cover with sufficient absorbent capacity and capillary suction to successfully compete with the suction pressure of a superabsorbent-containing core to maintain a soft, lubricious condition during use. Unfortunately, these three attempts provide a conventional capillary suction pressure gradient which strongly draws liquids into the tampon using covers which may themselves sufficiently dry the squamous epithelium to cause pain and trauma during use.
A different approach is disclosed in Foley et al., EP 685215, which reduces the capillary suction pressure that a tampon exerts on the vaginal walls to remove excess menstrual fluid while limiting the vaginal drying which can occur. This may be accomplished by using multiple cover layers, possibly hydrophobic, to separate the absorbent core from the vaginal wall during use. While this advance is significant, the outer surface of the tampon is likely to be relatively dry.
Therefore, what is needed is a tampon having reduced suction pressure to avoid drawing too much of the natural moisture from the squamous epithelium and which maintains a moist outer surface throughout use to provide a non-drying tampon for catamenial use.
Understanding the discomfort and pain associated with tampon insertion and removal has led to the invention of a tampon which keeps the vaginal wall naturally moist. The unique structure of this improved cover substantially reduces vaginal drying by maintaining the natural moisture of the vaginal wall. Additionally, insertion and removal comfort can be further enhanced by a smooth surface presented by the outer layer of a multilayered cover.
Thus, the present invention relates to a tampon having an absorbent structure and a multilayered cover substantially enclosing the absorbent structure. The cover has an outer layer capable of retaining liquid and an inner layer disposed between the outer layer and the absorbent structure. The inner layer creates a controlled interruption of fluid flow between the outer layer and the absorbent structure. This interruption allows the outer layer to retain sufficient liquid to minimize vaginal wall desiccation/drying prior to saturation of the absorbent structure.